Internal combustion engine with subcombustion chamber



United States Patent [72] Inventors Toshio Suzuki, Nagoya-shi,

Yujiro Oshima, Ichinomiya-shi, and Masao Kataoka, Nagoya-shi, Japan [21Appl. No. 772,732

[22] Filed Nov. 1,1968

{45] Patented Dec. 1, 1970 [731 Assignee Kabushlki Kaisha Toyota ChuoKenkyusho,

Nagoya-5111, Aiehl-ken, Japan [32] Priority Nov. 18, 1967 [33] Japan[54] INTERNAL COMBUSTION ENGINE WITH SUB- l23/l19 l23/l 19 123/75ABSTRACT: An internal combustion engine having a cylinder, including amain combustion chamber, in combination with a subcombustion chamberprovided with an ignition plug and communicating with the maincombustion chamber through a small hole in a cylinder wall for jettingout the flame of air-fuel mixture ignited in the subcombustion chamberto the main combustion chamber, the air-fuel mixture being supplied tothe subcombustion chamber through a suction tube from the samecarburetor which feeds the main combustion chamber. The carburetor inletof said suction tube is positioned between the throttle valves of acarburetor having dual throttle valves. A valve is placed at the outletof the suction tube to the subcombustion chamber and this valve may beinterconnected with a main valve in the suction manifold leading fromthe carburetor to the main combustion chamber to move in synchronismtherewith and with a piston in the cylinder, or it may be arranged tooperate automatically in response to the difference of pressure withinthe subcombustion chamber and the suction tube.

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The present invention relates to improvements in an internal combustionengine provided with a main and a subcombustion chamber, the latterbeing separated from the main combustion chamber by a wall andcommunicating with the main combustion chamber through a small hole, orholes, so that upon ignition of fuel-air mixture in the subcombustionchamber the resultant flame will jet out into the main combustionchamber and ignite fuel-air mixture therein.

In the most common conventional internal combustion engine, air-fuelmixture is supplied from the carburetor to the combustion chamber formedin the cylinder above the piston, and the mixture is ignited by a sparkplug within the combustion chamber to give motion to the piston, butsome exhaust gas remains in said chamber even after the piston arrivesat the top dead centerduring the exhaust stroke. Subsequently, air-fuelmixture sucked into the combustion chamber during the suction stroke isdiluted by the remaining exhaust gas, particularly when theproportionate amount of inhated air is reduced in relation to the fuelas the throttle valve in the carburetor is almost closed underno-loadrunning condition. This further reducesthe efficiency of combustion byincreasing the remaining unburned fuel in the exhaust, and generatesinjurious components in the exhaust.

Therefore, it has been proposed to modify the engine by adding asubcombustion chamber having a spark plug and a small suction valve tothe above mentioned combustion chamber, hereinafter termed the maincombustion chamber, and rich air-fuel mixture is sucked from acarburetor to the subcombustion chamber for ignition and burningtherein. As a result, the air-fuel mixture in the main combustionchamber, although excessively diluted by residual gas, is burnt by theflame jetted out from the subcombustion chamber into the main combustionchamber.

In the above described modified conventional internal combustion engine,independent carburetors are provided for the main and subcombustionchambers, and since the amount or air-fuel mixture fed into thesubcombustion chamber is smaller than the amount fed to the maincombustion chamber, the carburetor for the subcombustion chamber must bemade considerably smaller than the carburetor for the main combustionchamber. In addition, it is necessary to provide a throttle valve in thesmaller carburetor as in the carburetor for the main combustion chamberbecause the feed of air-fuel mixture must be controlled for meetingvarious kinds of driving conditions.

Regardless of the change in amount of the air supplied to thesubcombustion chamber, it has been necessary to provide a fuel supplyingauxiliary carburetor device almost identical with the carburetor for themain combustion chamber, because it is necessary to retain the air-fuelratio to be always within a proper range and, therefore, it isimpossible to avoid complicating the auxiliary carburetor structure iffuel combustion is to be improved.

It is a primary object of the present invention to provide an improvedengine construction embodying .main and subcombustion chambers whichwill obviate the defects and disadvantages of conventional engines asbriefly outlined above.

It is an important object of this invention to provide an internalcombustion engine with a subcombustion chamber and related parts whichwill improve combustion efficiency and prevent the generation ofinjurious components in the exhaust gas under any and all driving statesand conditions.

It is another important object of this invention to provide an internalcombustion engine with subcombustion chamber wherein the air-fuelmixture which is ignited and burned in the subcombustion chamber issupplied from the same carburetor which supplies the main combustionchamber.

A further object of this invention is to provide an internal combustionengine with subcombustion chamber wherein the supply of air-fuelmixtureto the subcombustion chamber is properly regulated under any and alldriving states.

Yet another object of the invention is to provide an improved internalcombustion engine with subcombustion chamber, having the above describedcharacteristics, which is of simple construction, and easy andeconomical to manufacture and use.

In accordance with the present invention, it is not necessary to providea separate carburetor for the subcombustion chamber, the air-fuelmixture being introduced into the subcombustion chamber from the samecarburetor supplying the main combustion chamber. The mixture is ignitedby an ignition plug within the subcombustion chamber to burn therein andthe resultant flame is jetted into the main combustion chamber through asmall aperture in the wall separating the two chambers. Thus, thestructural drawback of providing an additional carburetor in theconventional engine with subcombustion chamber is removed, and at thesame time, a proper mix of air and fuel is always supplied from thecarburetor which feeds the main combustion chamber. With the new device,it is possible to obtain excellent combustion in any driving state ofthe engine.

To enable this result in the internal combustion engine of the presentinvention, air-fuel mixture is fed to the subcombustion chamber by asuction tube leading from the main carburetor to the subcombustionchamber. One end of the tube opens to the interior of the carburetorbetween its two throttle valves, which are provided downstream of theventuri portion of the carburetor. The other end of the suction tube isconnected to the suction opening of the subcombustion chamber. In thismanner excellent regulation of fuel-air mixture supplied to thesubcombustion chamber is effected, and perfect and uniform subsequentcombustion ofthe mixture gas within the main combustion chamber can bemade. The present invention is particularly effective in increasedefficiency of combustion under no-load running, the imperfect combustionof the excessively diluted mixture gas within the main combustionchamber being completely avoided and the generation of injuriouscomponents ofthe exhaust gas being prevented.

The novel features that are considered characteristic of the inventionare set forth with particularity in the appended claims. The invention,itself, however, both as to its organization and its method ofoperation, together with additional objects and advantages thereof, willbest be understood from the following description of specificembodiments when read in connection with the accompanying drawings,wherein like reference characters indicate like parts throughout theseveral FIGS. and inwhich:

FIG. 1 is a sectional diagram illustrating an embodiment of theinvention;

FIG. 2 is a fragmentary sectional diagram showing a portion of thecarburetor of FIG. 1 in a plane at right angle to the view of FIG. 1;

Referring now more particularly to the drawings, and in the embodimentas shown in FIGS. 1 and 2, A generally represents the carburetor and Bthe upper portion of the cylinder provided with the subcombustionchamber. The carburetor is connected to the upper portion 4 of thecombustion chamber above the piston 2 within the cylinder 1, by suctionmanifold 17, and the carburetor A and the subcombustion chamber 21 areconnected by a suction tube 25.

In the internal portion of the cylinder head 3, fixed on the upperportion of the cylinder 1, the main combustion chamber 4 is formedbetween the cylinder head and the upper surface of the piston 2 whichreciprocates within the cylinder 1, and the air-fuel mixture supplied bythe carburetor A is sucked through the opening 5 at the end of themanifold 17.

Opening 5 is opened or closed by the valve 6 whose stem protrudes abovethe cylinder head and bears against one end ofa pivoted rocker arm 31,the other end of which is interconnected through a conventionalmechanism with thepiston 2 and regulates the amount of the air-fuelmixture sucked into the main combustion chamber, Valve 6 is resilientlybiased closed by the unnumbered spring shown, said bias being overcomeon downward movement of the right end of rocker arm 31.

The main nozzle 9 of the carburetor A, for supplying fuel from the fuelsource into the venturi portion 8 downstream of the choke valve 7, isopened and the primary throttle valve if and the secondary throttlevalve 12 which are respectively interconnected and move together inresponse to the operation of the accelerator pedal, are provideddownstream of said main nozzle 9.

The opening of the primary throttle valve 11 is adjusted to be slightlylarger than the opening of the secondary throttle valve 12. These valvesare respectively rotated by shafts i3 and 14 and interconnected byconnecter 16 to the throttle lever controlled by the accelerator pedal,not shown.

Passage 10 for supplying fuel during low speed drive opens to theinternal wall of the carburetor just below the primary throttle valve11, and one end 27 of the suction tube 25 for supplying the air-fuelmixture into the subcombustion chamber 21, opens into the carburetorbore between the valves it, 12 andjust downstream of passage 10.

The subcombustion chamber 21 has inserted therein the igniting sparkplug 23 including electrode 24 which is energized in a conventional wayby a source of electricity and ignition current (not shown). Chamber 2)!is integrally formed in a sidewall of the cylinder head 3, thesubcombustion chamber 21 and the main combustion chamber 4 beingconnected by the small hole, or holes, 22 through the wall separatingthem.

The subcombustion chamber 21 has a suction opening for inlet of air-fuelmixture supplied through the suction tube 25, one end 27 of the suctiontube 25 opening within the carburetor as previously explained, and theother end 26 thereof opening through an outer sidewall of thesubcombustion chamber 21. Suction tube 25 passes through the exhaustmanifold 29 connected to the main combustion chamber. The said suctionopening 20 is compulsorily opened and closed, synchronizing with thesuction valve 6 of the main combustion chamber by means of theresiliently biased-to-close valve 30 whose protruding stem bears againstthe same end of rocker arm 31, but closer to its pivot so as to beproportionately moved to open in interconnected fashion with main valve6.

The above described device operates in the following manner: When theinternal combustion engine is operated in slow drive, the opening of theprimary throttle valve 11 is small, and the secondary throttle valve 12is almost totally closed. Fuel is jetted from the passage 10 to the end27 of the suction tube 25. During the suction stroke, the valve 6 of themain combustion chamber is opened, and the piston 2 is lowered withinthe cylinder 1 to suck the air-fuel mixture into the cylinder, but sincethe secondary throttle valve 12 is almost totally closed, the pressurewithin the main combustion chamber is lowered. At the same time, therich fuel-air mixture from the passage 10 is sucked into the end 27 ofthe suction tube 25, provided just below said passage 10, and flows intothe subcombustion chamber 21 because the suction valve 30 opens as aresult of movement of rocker arm 31. The pressure of the fuel-airmixture in the subcombustion chamber is raised higher than that of thefuel-air mixture within the main combustion chamber 4, and, therefore,the exhaust gas remaining within the subcombustion chamber 21 is drivenout into the main combustion chamber 4. The fuel-air mixture in chamber21 is, therefore, relatively undiluted by exhaust gas, and is ignited bythe electrode 24 of the ignition plug to burn perfectly, the flame beingjetted out from the small hole 22 into the main combustion chamber 4%.The ignition energy of this flame is great, and consequently, the fuelmixture in the main combustion chamber 4, even though excessivelydiluted by exhaust gas, is burned perfectly.

During full load drive condition most ofthe fuel-air mixture is suckedinto the main combustion chamber 4 because both the primary throttlevalve 11 and the secondary throttle valve 12 are fully open. Thefuel-air mixture within the main combustion chamber a flows into thesubcombustion chamber 21 through the small hole 22 because ofthe higherpressure in the main chamber. The ignition plug again ignites themixture in the subcombustion chamber and the flame is convectionallyjetted into the main combustion chamber 4 to burn the fuel therein.Since the amount of the fuel-air mixture sucked into the main combustionchamber 4 is great, the remaining exhaust gas is proportionately smalland has little effect. Thus, combustion takes place, ignited by theflame from chamber 21. through opening 22, perfectly and uniformly.

Under part load condition, the primary throttle valve it is half opened,and the secondary throttle valve 12 is somewhat less opened than theprimary throttle valve. The amount of the fuel-air mixture to be suckedinto the subcombustion chamber 21 through the suction tube 25 isdetermined by the difference of the pressure of the gas within thesuction tube 25 and within the suction manifold 17 in accordance withthe opening or setting of the secondary throttle valve 12. The fuel inthe subcombustion chamber Zl is ignited in the same manner as explainedfor the preceding two instances, the fuel-air mixture within the maincombustion chamber 4 being ignited by the flame issuing from within thesubcombustion chamber 21 and then burning completely and perfectly.

in the foregoing embodiment, the opening of the primary throttle valveis a little larger than the opening of the scconda ry throttle valve,but insteadthe two throttle valves can be arranged to open to the samedegree.

Because the suction tube 25 for the subcombustion chamber is passedthrough the exhaust manifold 29, the fuelair mixture supplied into thesubcombustion chamber 22 is preheated, and the combustion within thesubcombustion chamber 21 is thus accelerated.

During condition of full load running, the amount and the pressure ofthe mixture to be supplied to the main combustion chamber 4 throughmanifold 17 are increased and, therefore, the automatic suction valve30' of the subcombustion chamber 21 is not opened, and no, or verylittle fuel-air mixture passes into the subcombustion chamber 21 fromtube 25, but the fuel mixture under high pressure in the main combustionchamber 4 is jetted into the subcombustion chamber 21 through opening22, and is ignited and burned therein, the flame being jetted back outinto the main combustion chamber to ignite the fuel mixture therein.

The suction valve of the subcombustion chamber can be either anautomatic valve operated by the difference of pressures at the inlets tothe main and subcombustion chambers, or a valve interlocked tocompulsorily open and close with the main valve 6 regardless of thecarburetor construction.

it will be apparent that the invention functions to carry out perfectand uniform combustion, and especially when the fuelair mixture in themain combustion chamber is lean, or when it is excessively diluted byremaining exhaust gas tending to cause imperfect combustion, as inlo-load running. in this invention, the air-fuel mixture supplied to thesubcombustion chamber is properly regulated so as to quickly ignite andburn with great intensity, and its flame is jetted out into the maincombustion chamber to carry out the perfect combustion.

Moreover, in accordance with the present invention, airfuel mixture issupplied to the subcombustion chamber from the same carburetor whichsupplies mixture to the main combustion chamber, and, therefore, thestructure is simple, yet the mixture supplied to the subcombustionchamber is readily adjusted and regulated in accordance with the drivingstate by normal operation of the carburetor throttle.

Thus, when the present invention is employed, improved economy of fueland the reduction of injurious components contained in the exhaust gascan be obtained.

Although a certain specific embodiment of the invention has been shownand described, it is obvious that many modifications thereof arepossible. The invention, therefore, is not intended to be restricted tothe exact showing of the drawings and description thereof, but isconsidered to include reasonable and obvious equivalents.

We claim:

An internal combustion engine having, in combination, a main combustionchamber ina cylinder communicating with a manifold, a subcombustionchamber separated from said cylinder by a wall, said subcombustionchamber communicatpassage, the secondary throttle valve being positioneddownstream of said primary throttle valve and said'pair of throttlevalves being operated in interconnected fashion with each other, one endof said tube opening into said carburetor at a position between'saidpair of throttle valves and just below said passage for supplyingfuel toreceive fuel jetted from said passage when the secondary throttle valveis almost totally closed, and'the other end of said tube having anoutlet to the subcombustion chamber controlled by a suction valve.

